ScotRail have been forced to cancel their Santa Express trips last minute due to new guidance on coronavirus.
The events had been scheduled to take place on Saturday and next weekend on the Fife Circle line.
Tickets for the Santa Express sold out within hours, with all proceeds going to the Railway Children Charity which supports vulnerable children who live alone and at risk on the streets.
ScotRail said on Friday evening: "Sadly, due to updated guidance on coronavirus by the Scottish Govt, we have no option but to cancel all 4 Santa Express trips around the Fife Circle tomorrow & 18 December.
"We know how disappointing this will be, but the health & well-being of everyone is our priority."
The Santa Express is a festive train decked out in Christmas decorations and would have been departing from Edinburgh Waverly to travel across the Forth Road Bridge and around the Fife Circle.
Father Christmas was due to be walking up and down the carriages handing out gifts to children aboard.
It's another blow for ScotRail on Friday after 60 services were cancelled due to rising levels of self-isolation amongst staff.
This is mainly affecting services across the central belt of Scotland and the rail operator says its social media channels will be providing up-to-date information.
ScotRail added: "Santa is just as upset as you will all be, but he’s arranging for you to get a full refund or showing how you can donate your fare in full to the Railway Children charity. An email will arrive with you later tonight explaining what you need to do.
"Santa had arranged for some very special gifts for our younger passengers and we will be donating these to a number of children's hospitals and hospices across Scotland, to ensure that they are put to good use."
READ MORE: Dozens of ScotRail services cancelled due to rapid spread of Covid
People were told to "think a bit more carefully" about unnecessary social contacts and defer work Christmas parties amid forecasts that the highly transmissible Omicron variant will become dominant in Scotland within days, by Nicola Sturgeon today.
From tomorrow restrictions will be tightened to require all household contacts of anyone who tests positive for Covid - even if they are not identified as an Omicron case - to self-isolate for 10 days regardless of vaccination status.
Non-household contacts of any Covid positive case can end isolation if they receive a negative PCR result, as long as they are fully vaccinated.
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